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Wageningen University

What exactly is astaxanthin and why does it make salmon red?

Astaxanthin is the red pigment that gives salmon, shrimp and flamingos their pink-red colour. Chemically it is similar to ß-carotene (in carrots) and vitamin A. It is part of the group of carotenoids. The chemical structure of astaxanthin is shown below:

Astaxanthin is made by several kinds of algae and plankton. These are eaten by many aquatic species including crustaceans, amongst which are shrimps, which store the pigment in their shell, resulting in their pink-red exterior. Crustaceans in turn are eaten by fish (salmon, trout) or birds (flamingo, red ibis). These also store the pigment in their skin and fatty tissue. This is the reason why salmon and other animals are red. Astaxanthin does not undergo bleaching, thus these animals retain their pink coloration.

The function of astaxanthin in connection with aquatic animals is not entirely clear. However, it is a potent antioxidant, comparable to vitamin E. It may also offer protection against UV light.

Only algae can produce astaxanthin; higher animals cannot alter the chemical structure. This has important consequences for aquaculture (fish farming).

Salmon farming exists in several forms. Salmon can be grown in the sea, where their diet is partly natural, but they also get additional food. Another way to culture salmon is in tanks on land. In this case they do not eat a natural diet, but get fish feed. However, without shrimp or another source of astaxanthin, salmon will remain white. The consumer does not want this, which means astaxanthin will have to be added to the fish feed

Astaxanthin is chemically made from carotene. This is the most common source of astaxanthin in fish feed. Other possibilities are: adding shrimp waste or adding a powder made from astaxanthin-producing yeasts. However, the last two methods are considerably more expensive, which is why the chemically made astaxanthin is mainly used.

It is chemically different (mirror image of the natural astaxanthin) but for salmon or men it makes no difference.